Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$68.73	5.598%	$72.5775	$72.58	$72.60	$72.60
Purchase #2	$44.31	4.565%	$46.3328	$46.33	$46.35	$46.30
Purchase #3	$76.29	9.571%	$83.5917	$83.59	$83.60	$83.60
Purchase #4	$50.63	6.851%	$54.0987	$54.10	$54.10	$54.10
Purchase #5	$242.41	10.868%	$268.7551	$268.76	$268.75	$268.80
Purchase #6	$58.29	8.744%	$63.3869	$63.39	$63.40	$63.40
Purchase #7	$110.35	12.271%	$123.891	$123.89	$123.90	$123.90
7 purchase totals =	$651.01		$712.6337	$712.64	$712.70	$712.70